Biochemical evaluation of an infant with hypoglycemia resulting from a novel de novo mutation of the GLUD1 gene and hyperinsulinism-hyperammonemia syndrome.

Hyperinsulinism-hyperammonemia syndrome (HI/HA) (OMIM 606762), the second most common form of congenital hyperinsulinism (CHI) is associated with activating missense mutations in the GLUD1 gene, which encodes the mitochondrial matrix enzyme, glutamate dehydrogenase (GDH). Patients present with recurrent symptomatic postprandial hypoglycemia following protein-rich meals (leucine-sensitive hypoglycemia) as well as fasting hypoglycemia accompanied by asymptomatic elevations of plasma ammonia. In contrast to other forms of CHI, the phenotype is reported to be milder thus escaping recognition for the first few months of life.